hmSOD1 gene mutation‐induced disturbance in iron metabolism is mediated by impairment of Akt signalling pathway

Abstract

BackgroundRecently, skeletal muscle atrophy, impairment of iron metabolism, and insulin signalling have been reported in rats suffering from amyotrophic lateral sclerosis (ALS). However, the interrelationship between these changes has not been studied. We hypothesize that an impaired Akt–FOXO3a signalling pathway triggers changes in the iron metabolism in the muscles of transgenic animals.MethodsIn the present study, we used transgenic rats bearing the G93A hmSOD1 gene and their non‐transgenic littermates. The study was performed on the muscles taken from animals at three different stages of the disease: asymptomatic (ALS I), the onset of the disease (ALS II), and the terminal stage of the disease (ALS III). In order to study the molecular mechanism of changes in iron metabolism, we used SH‐SY5Y and C2C12 cell lines stably transfected with pcDNA3.1, SOD1 WT and SOD1 G93A, or FOXO3a TM‐ER.ResultsA significant decrease in P‐Akt level and changes in iron metabolism were observed even in the group of ALS I animals. This was accompanied by an increase in the active form of FOXO3a, up‐regulation of atrogin‐1, and catalase. However, significant muscle atrophy was observed in ALS II animals. An increase in ferritin L and H was accompanied by a rise in PCBP1 and APP protein levels. In SH‐SY5Y cells stably expressing SOD1 or SOD1 G93A, we observed elevated levels of ferritin L and H and non‐haem iron. Interestingly, insulin treatment significantly down‐regulated ferritin L and H proteins in the cell. Conversely, cells transfected with small interfering RNA against Akt 1, 2, 3, respectively, showed a significant increase in the ferritin and FOXO3a levels. In order to assess the role of FOXO3a in the ferritin expression, we constructed a line of SH‐SY5Y cells that expressed a fusion protein made of FOXO3a fused at the C‐terminus with the ligand‐binding domain of the oestrogen receptor (TM‐ER) being activated by 4‐hydroxytamoxifen. Treatment of the cells with 4‐hydroxytamoxifen significantly up‐regulated ferritin L and H proteins level.ConclusionsOur data suggest that impairment of insulin signalling and iron metabolism in the skeletal muscle precedes muscle atrophy and is mediated by changes in Akt/FOXO3a signalling pathways.

Exercise Training and Vitamin C Supplementation Affects Ferritin mRNA in Leukocytes without Affecting Prooxidative/Antioxidative Balance in Elderly Women

“…Furthermore, FOXO3a and CAT have apoptosis-regulation properties [28,29]. Recently it has been shown that FOXO3a controls the expression of ferritin and catalase mRNA [30,31], thus the next goal of this study was to determine the effect of training and supplementation on the expression of these genes. Unfortunately, no significant changes were observed for FOXO3a and CAT mRNA.…”

Swim Training Modulates Skeletal Muscle Energy Metabolism, Oxidative Stress, and Mitochondrial Cholesterol Content in Amyotrophic Lateral Sclerosis Mice

“…Numerous studies have found evidence of increased oxidative stress in ALS pathogenesis. More oxidative damage was also observed in the skeletal muscle of ALS animal models [ 3 , 53 – 55 ]. Some authors suggested that oxidative stress prevention is a key element in neuroprotection in ALS and other neuromuscular disorders [ 56 , 57 ].…”

The Contribution of Iron to Protein Aggregation Disorders in the Central Nervous System

“…In vitro studies analyzing cell lysates showed an increased iron content and altered iron metabolism mediated by an impaired Akt signaling pathway. Accordingly, SOD1.G93A overexpression triggered an inactivation of Akt, activation of the transcription factor FOXO3a and subsequently increased ferritin synthesis and iron accumulation (Hadzhieva et al, 2013; Halon-Golabek et al, 2018). SOD1.G37R mutants showed in vivo and in vitro increased mRNA levels of TfR1, ferritin, DMT1 but also of mitochondrial ferritin (Jeong et al, 2009).…”